Method of operating gaseous thermionic tubes



Patented May 11, 1948 as T T-as orries "METHOD OF"OPERATING"GASEOUSTHE'RMIONIC TUBES Montford Morrison, Upper Montclair N. J.

Application October 128, 1943, Serial No.-'50'1,975

3 Claims.

This invention relates to methods of operating certain gaseousther-mionic' tubes which have a control eletztroda-an-andde and acathode, and relates in particular to methods employed in telecontrolcircuitsandhasspecific relation toelectronio-re'lays.

Among the objects of the invention are: to provide a-method of operatingan electrode controlled gaseous thermionic tube as a direct currentrelay; to provide sucha method with operational current characteristicswhic'hclosely parallel mechanical relay operation, toprovide in such amethod a way 'that'does not necessitate the employment ofmechanicalcontacts; and to provide --a-met-hod having such objects that is simpleand reli able.

*In'the' prior art;gaseous triodes have been used in oscillatorycircuits, particularly those referred toas relaxation circuits. 5 Inthese circuits the plate current is always of a pulsating form and thecircuitso operates that thegaseous discharge in the tube isex'tinguishedafter each impulse by reason or the plate voltage beingreduced and held below the ionization voltage of the tube or byreason ofthe plate circuit being of an osciliatorychara'ct'er in which the platevoltage may beactually reversed at the end of one half-period of theplate circuit. a

I have discovered that gaseous conduction electrode control tubes may beselectedand oscillatory circuits so fitted to them that an entirelydifferent operation is achieved.

According to this discovery, I may select a gaseousdischarge electrodecontrol tube supplied with a direct current source of power andoperating-a mechanical relay or other translating device,-and byproperly fitting the input circuit; in-

cluding the control grid, to the output circuit including the plate, Iprovide a method of operation of the said tube whereby the plate currentassumes a constant unvarying value so long as the proper input voltageis applied to the controlgridand bythe removal of this control gridvoltage the circuit is set into oscillation in such a way as toextinguish the discharge through the said tube causing the said tube tooperate in a manner similar to a direct current relay.

This provides a relay action for a make and 7 break circuit, utilizingdirect current and providing an extremely high amplification: factor.

Other and further objects will be pointed out and obvious'in the readingof the description hereunder, particularly when taken inconnectionwith'the drawings in which Figure 1 is an actual workingdrawing illustrating one embodiment of the inventiom-and Figure 2 is agraph useful in understanding the operation thereof. Reierring'tdFl-g:1, l is a ground-lead between which lead and lead' 2' is supplied a makeand break input voltage; common to telegraphcircults. 3 -is-a switch'whichgwhen closeihbridges the input circuit with-a 5000 ohmwire wound.p tentiometer d. 5 represents thepbtentiometer armwhich is connected tothe grid of -a gaseous discharge electrode'controlledtube*6,'thespecific one illustrated being a mercury vapor triode known asl28,'andsold by theNational Union Radio-Corporation of New Yo'rk'in1936.

The cathode of tube 6 has connected in its grid circuit-a 25 000ohm-wire wound potentiometer-l, for biasing the gridof "said-tubeandwhich potentiometer is bridged by -a 22.5 volt battery *8. The platelead 9 has connected in it asa-load, a ohm main line-sounderiii,- of astandard construction, commonly usedby the telegraph companies, and saidsounder is shunted by a .25 mi. condenser ll. Plate lead Sihasconnectedin series with it,'a SOOO-ohm' current limiting resistor l2 whichclosesthe 'CilGlJfit' of the 300 volt plate power supply 13. *Condenseris connected between the relay l0 and the resistor l2 in the platecircuit andthencetethefiroundlead- I and isa 2 m'f. condenser.

The tube'fi may in efiect'be-anyof thegaseous dischargeelectron'controlled tubes containing any suitable gas, theonly-requirement being" that it is so selecte'dthat itscharacteristics'come'within those required for the method of operationhereunder claimed.

The abovedescribed circuitfina-ppBarance is related to acommon,gaseoustrioderelaxation oscillator classification and thediscovery herein described relates to the method operating-such acircuitin-a novel and useful'manner.

Inorder to avoid obscuring the teaching of a practical embodiment of"the discovery by generaliz'ingupon the circuit =fu-nctions, "thespecific circuit above described-willbe discussdand the generalitiesrelating thereto-will be set forth in the claims hereunder.

zit-has beenknown in theart that" gaseous triodes are very subject tosetting up oscillations when connected in certain types of oscillatorycircuits but theseosc'illations have -heretofore been very detrimentalto the operation of the tube and if allowed to exist undericontinuedoperation they ,quite oftengandusually do result in-a'destruction of thetube cathodedue to excessive operation imposed upon the cathodeunderthese conditions.

I have discovered that this tendency to oscillate, if utilized in amethod-ofoscillationwhereby the oscill-ationsset up are of aweryishortduration at only periodic intervals, that the tube is .not harmedtherebyand further, this oscillatory effect can be utilized toextinguish thegaseous discharge through the tube, thereby providing anovel' and useful'application for'a phenomenon which'has' heretoioreflresulted chiefly in the destruction of theoperable usefulness of the"tube.

If the exact circuit is set up as above described and the potentiometer1 is set up to a bias sufficient to prevent the voltage source l3 fromproducing gaseous ionization through the tube and then switch 3 closedto provide sufilcient voltage by adjustment of potentiometer arm 5 tocause gaseous discharge through tube 6, and then by opening switch 3 andreadjusting potentiometer arm 5, there will be found a not too criticalpoint at which the plate circuit begins to oscillate with the resultthat the gaseous discharge through the tube is completely extinguished.

Several repeated trials of adjustment may be required, includingchanging the positions of the potentiometer arms of potentiometers 4 andl to find the optimum settings to give the most satisfactory result, butfinally a setting will be found for at least one range of temperaturesof the gas in tube 6 whereupon closing switch 3, gaseous dischargethrough tube 6 is initiated, which is constant in value and withoutoscillations therein and upon the opening of switch 3 the gaseousdischarge through tube 6 is extinguished by oscillations set up in thecircuit of plate 9.

Referring to Fig. 2, curve I4 represents the constant value of the platecurrent in lead 9 with a properly adjusted steady state bias which isthe algebraic sum of the negative bias acquired through potentiometer 'land a positive voltage acquired through potentiometer 4, which showsgraphically the operation described above. This operation continues to apoint i 5 on curve 14 at which time switch 3, Fig. 1, is opened,allowing the negative bias to increase to the value 2|, Fig. 2. Theplate current begins to oscillate in accordance with the graph in Fig.2, beginning at point 15 with increasing oscillations until the valuethereof reaches a point 16, which is twice the value of l4 orthereabouts, and upon the succeeding negative half cycle of the saidoscillations, the negative voltage has caused the plate voltage of tube9 to recede to a point below the ionization voltage of the tube, or inmost cases, to an actual negative value at which time the gaseousdischarge is extinguished.

The length of time required for the tube to extinguish the gaseousconduction depends entirely upon the frequency of these oscillations andthe rate at which they can build up, illustrated in Fig. 2, betweenlines 18 and I9 as being .002 second, assuming the period Of oscillationto be 1000 cycles, as illustrated in the figure.

In actual practice, this period, represented by the distance between itand 19, can be made much shorter if and when desired, by properlyselecting the frequency at which the tube oscillates out and the rate atwhich the amplitude of the frequency employed in oscillating out, isable to build up.

With this bias set at the value of 2|, Fig. 2, in so far as additionaloscillations are concerned, it will be appreciated by those skilled inthe art, that the tube will not oscillate after the plate current hasbeen once extinguished and therefore this oscillatory condition ispresent in the tube for only a very short interval of time as comparedto the total working time of the tube and therefore does no practicalharm to the tube under these conditions.

After the tube has oscillated out at point 11, the plate current remainsat zero until switch 3, Fig. 1, is again closed at a later timerepresented by line 22, Fig. 2, at which time gaseous conduction isinitiated through the tube and the I by defined to be one in which,after the ga has become ionized, the grid ordinarily has no furthereffect on the flow of plate current, that is. one in which, when thetube is operating with a direct plate voltage in series with a resistiveload and a direct voltage control in the grid circuit, that the platecurrent cannot be extinguished by an adjustment of the grid bias. Thisis the normal form of gaseous thermionic tubes and is the type commonlyknown commercially as Thyratrons and Grid-Glow tubes.

Having fully described one embodiment of my invention in very specificdetail, the generalities and scope of the invention are set forth in theclaims hereunder.

What I claim is:

1. The method of operating a normal gaseous thermionic tube which has acontrol electrode, a cathode, and an anode, said tube having a plateresistance under cathode-current conduction independent of a first rangeof cathode-controlelectrode-bias parameters when connected to acathode-plate-voltage circuit having oscillatory constants and having anegative resistance characteristic under a second range ofcathode-control-electrode-bias parameter when connected to said circuit,which method comprises setting said parameters within said first rangecausing said circuit to pass a non-oscillatory current and then settingsaid parameters within said second range causing said circuit to pass anoscillatory current.

2. The method of operating a normal gaseous thermionic tube which has acontrol electrode, a cathode and an anode, which comprises subjectingsaid control electrode to connected circuits having parameters causingcontinuous conduction tube current and then subjecting said controlelectrode to connected circuits having oscillatory parameters causinginterruption of said current.

3. The method of operating a normal gaseous thermionic tube which has acontrol electrode with a predetermined voltage bias, a cathode, and ananode, which comprises causing said tube to pass a continuousunidirectional current to a load circuit for an arbitraiy duration oftime, and then adjusting said bias causing said tube and said loadcircuit to provide oscillatory current which functions to extinguishsaid load current.

MONTFORD MORRISON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,919,251 Page July 25, 19331,979,054 Scheer Oct. 30, 1934 2,038,683 Schr-amm Apr. 28, 19362,092,851 Osgood Sept. 14, 1947 2,100,700 Schlesinger Nov. 30, 19372,114,016 Dimond Apr. 12, 1938 2,315,733 Ffleger Apr. 6,1943

